The storm of noise from the grandstand as Camelot set off in pursuit of Encke in the final furlong of the Ladbrokes St Leger dropped away to near-silence a few strides from the line, as it became clear that the 2-5 favourite was about to come up short in his pursuit of the Triple Crown.

Camelot still had three-quarters of a length to find as Encke passed the post to win the season's final Classic for Godolphin, and the hush on the terraces was swiftly replaced by the buzz of 32,000 spectators asking how and why the Derby winner had been beaten.

Whenever a hot favourite is still closing on the winner at the line, the fingers will point first at the jockey, and the look on the face of Joseph O'Brien, Camelot's 19-year-old rider, as he returned to unsaddle seemed to suggest that he was doing the same.

Throughout the first mile, Camelot was settled a good way off what turned out to be a modest pace, and the favourite, who travelled well throughout, then had to edge away from the rail in order to deliver his challenge.

When he did ask Camelot to quicken, though, O'Brien did not receive anything like the instant response from his partner that his cruise into the race implied. He was scarcely a length behind Encke as they both struck for home, but it was Encke, a 25-1 outsider, who produced an immediate response for his rider, Mickaël Barzalona. Camelot's head came up and he struggled to find top gear, gifting Encke a three-length advantage at a vital moment in the race.

While Camelot closed the gap steadily, it was a task too far for the previously unbeaten colt, who would have become the first winner of the Triple Crown since Nijinsky in 1970.

Joseph O'Brien was too upset to comment after the race, but his father Aidan, Camelot's trainer, said that he regretted his own decision not to run a pacemaker in the Classic.

"He was a little fresh with him and tanked a bit, but that was probably always going to happen in a slowly run race over that trip," O'Brien said. "You had to take your time on him over this trip, which he did, and then when he got out, he just stayed on rather than quickened.

"In the Guineas, he quickened. In the Derby, he quickened. Today he just stayed on. He ran a great race, and just got beat. It's disappointing for everybody that he got beat, but that's the way it is. That's racing. Everyone expected him to win, but that's life.

"If we'd thought that they were going to go that steady, I'd have had a pacemaker in, or two pacemakers. I was sure they were going to go a pace.

"The horse that won had a handier position and got the run, but the Camelot we know over a mile or a mile and a quarter would quickened up and got him, but today he didn't."

O'Brien added that he understood his son's decisions through the race. "Of course, Joseph was upset, no one thinks more about the horse than him," he said. "I can see as the race unfolded, where he went and why he went. He had to stay creeping where he was, he had to let gaps come as they did. If he'd been four wide coming into the straight, I'd have been going mad. "How many times do I do it [run a pacemaker] and make a hash of it? And now I don't do it, and I make a hash of it as well."

Encke, a son of Kingmambo out of an Irish Oaks winner, had finished only third behind Thought Worthy and Main Sequence, two of the also-rans on Saturday, in his last race, but showed improvement for the step up in trip and was a worthy winner.

"Two years ago we ran Rewilding and last year we ran Blue Bunting, who were both favourites," Mahmood al-Zarooni, the winning trainer, said. "Today, we have won it with an outsider. Racing can be a funny game.

"To be honest, it was [Sheikh Mohammed's] decision to run here today. I disagreed and thought we should not. He was right.

"I thought Camelot would catch us as I remembe red the way he quickened in the Guineas and the Derby [but] I knew Encke was tough and would keep going."

The winner is unlikely to run again this season, but will be kept in training as a four-year-old.

"He will be a lovely horse for next year," Simon Crisford, Godolphin's racing manager, said.

"We may be party poopers today, but we are happy to be party poopers."

Plans for Camelot, who was also attempting to give his trainer an unprecedented clean sweep in the five English Classics, will be considered over the next few days.